BB84 Quantum Key Distribution
Alice and Bob establish a secret key using polarized photons — detect Eve's interference
Photons:
20
Eve intercepts:
0%
Run Protocol
PHOTONS SENT
-
KEY BITS
-
QBER
-
EVE DETECTED?
-
PROTOCOL TRANSCRIPT (first 20 photons)
#
Alice bit
Alice basis
Photon
Eve basis
Eve reads
Bob basis
Bob reads
Basis match?
Key bit
ERROR RATE ANALYSIS
No eavesdropping (QBER≈0%)
With Eve (QBER≈25%)
Detection threshold (11%)